1. Field of the Invention
This invention relates to an optical information recording apparatus and method for recording and/or reproducing information on an optical information recording medium, and particularly to an optical information recording-reproducing apparatus and method for optical cards for effecting the recording and reproduction of information while an optical head and various optical cards are reciprocally moved relative to each other.
2. Related Background Art
Various mediums such as optical discs, optical cards and optical tapes are known as the forms of a medium for recording and reproducing information thereon by the use of light. These have their respective features and are used properly depending on purposes and uses, and above all, optical cards are expected to widen their use more and more in the future because of their features such as the ease of manufacture, good portability and good accessibility.
In each of these optical cards, it is usual that a plurality of tracking tracks are provided in parallel with to the longer sides of the card and the space between two adjacent tracking tracks is used as an information track for recording information thereon, and the tracking tracks are utilized as a guide for auto-tracking (AT) which controls an information recording-reproducing light spot so as not to deviate from a predetermined information track when the light spot scans the information track during the recording and reproduction of information. In the actual recording and reproduction of information, utilization is also made of auto-focusing (AF) which controls the light spot so as to be properly focused on the surface of the recording medium. Such AT and AF are popular techniques which have heretofore been often used in apparatuses using light to effect the recording and reproduction of information.
FIG. 1 of the accompanying drawings is a schematic plan view of such an optical card 101. Reference numeral 102 designates an information recording area, reference numeral 103 denotes an information track, reference numerals 104 and 104' designate track selection areas, and reference numeral 105 denotes the home position of a light spot. Reference numeral 106 designates an area in which a recording layer exists, and the home position 105 is included in this area.
Referring to FIG. 2 of the accompanying drawings, which is a block diagram showing an optical card information recording-reproducing apparatus according to the prior art, reference numeral 19 denotes an optical card information recording-reproducing apparatus (hereinafter referred to as the drive), and reference numeral 9 designates a CPU, which is a host control apparatus. The drive 19 is connected to the CPU 9 and executes recording and reproduction on the basis of a command issued from the CPU 9. The construction of the drive 19 is as follows. First, reference numeral 14 denotes a motor for introducing an optical card 1 into the drive 19 through a conveying mechanism, not shown, reciprocally moving the optical card 1 in the direction of arrow R at a predetermined location, and further ejecting the optical card outwardly of the drive 19. A sensor 50, for example, for optically detecting the optical card 1 is provided near the card insertion port (not shown) of the drive 19, and when the insertion of the optical card 1 is detected by the sensor 50, the optical card 1 is conveyed to a predetermined location in the drive, as previously described. Reference numeral 17 denotes a light beam applying optical system including a light source. During information recording and information reproduction, a light beam is applied from the light beam applying optical system 17 onto the optical card 1 and the light beam is reciprocally moved relative to the optical card 1 by the reciprocal movement of the optical card 1, and the light beam scans on the information track.
Reference numerals 28-30 designate photodetectors for receiving the reflected light of the light beam applied to the optical card 1, and recorded information is reproduced on the basis of the detection signals of these photodetectors. Reference numeral 15 denotes an AF actuator for driving a portion of the light beam applying optical system 17 to thereby move the focal position of the light beam spot on the surface of the optical card in the direction of arrow Z, i.e., the direction perpendicular to the surface of the optical card, and effect auto-focusing control, and reference numeral 16 designates an AT actuator for driving a portion of the light beam applying optical system 17 to thereby move the light beam spot on the surface of the optical card in a direction Y, i.e., a direction orthogonal to both of the direction R and the direction Z, and effect auto-tracking control. The light beam applying optical system 17, photodetectors 28-30, AF actuator 15 and AT actuator 16 are made integral with one another to constitute an optical head 18. Reference numeral 13 denotes a driving motor for moving this optical head 18 in the direction Y to thereby permit the light beam spot to have access to a desired track on the optical card 1.
Reference numeral 10 designates an MPU containing a ROM and a RAM therein. The MPU 10 controls various portions such as a card feeding motor 14 and a head feeding motor 13 and effects the communication and control of data with the CPU 9 under the control of the CPU 9. Reference numeral 11 denotes an AT/AF control circuit for driving the AF actuator 15 and the AT actuator 16 on the basis of the detection signals of the photodetectors 28-30 to thereby effect AF control and AT control. Reference numeral 12 designates a modulation-demodulation circuit for reproducing the detection signals of the photodetectors and demodulating the reproduced signals and reproducing them into original recording data. The thus obtained reproduced data are sent to the MPU 10, and are further transferred from the MPU 10 to the CPU 9. Also, during information recording, the recording data are sent from the MPU 10 to the modulation-demodulation circuit 12, in which the recording data are modulated by a predetermined modulation system. At this time, in the light beam applying optical system 17, the intensity of light of the semiconductor laser (not shown) of the light source is modulated in accordance with a modulation signal, and information by light modulation is recorded on the information track.
Reference numeral 71 denotes an encoder coupled to the driving motor 14. The encoder 71 outputs a pulse each time the driving motor 14 rotates by a predetermined angle. There is a predetermined relation between the angle of rotation of the driving motor 14 and the amount of movement of the optical card 1 in the direction R and therefore, by counting the output pulses of the encoder 71, the position of the light spot on the optical card 1 in the direction R can be detected. Reference numeral 72 designates a waveform shaping circuit for shaping the output pulses of the encoder 71 into a shape that can be received by the MPU 10. The CPU 9 instructs the drive 19 to record and reproduce the information of each sector, and in the drive 19, recording and reproduction are executed on the basis of these instructions.
FIG. 3 of the accompanying drawings is an exploded perspective view showing the internal construction of the optical head 18 in detail. In FIG. 3, reference numeral 20 denotes a light source for recording and reproduction such as a semiconductor laser. A light beam emitted from the light source is collimated by a collimator lens 21, whereafter it is divided into three light beams by a diffraction grating 23. These light beams are focused as light spots S1, S2 and S3 on the tracking track 37, the information track 39 and the tracking track 38, respectively, of the optical card 1 by an objective lens 26, as shown in FIG. 4 of the accompanying drawings.
The optical card 1 is reciprocally driven in the direction R indicated in FIG. 2, and the light spot and the optical card 1 are reciprocally moved relative to each other, whereby the light spot scans on the information track. The reflected lights of the light tracks S1, S2 and S3 again pass through the objective lens 26 and are reflected by a polarizing beam splitter 24, and are projected onto the photodetectors 28, 29 and 30, respectively, by a condensing lens system 27.
The condensing lens system 27 is an astigmatism system, and auto-focusing control by the astigmatism system is effected on the basis of the outputs of the photodetectors 28-30. FIG. 5 of the accompanying drawings shows the detecting surfaces of these photodetectors 28-30. The middle photodetectors 29 is a four-division sensor of which the detecting surface is divided into four detecting pieces A, B, C and D, and the photodetectors 28 and 30 on both sides thereof are ordinary sensors. Also, in FIG. 3, reference numeral 22 designates a prism for converting the cross-sectional distribution of the collimated light beam from an ellipse into a circle, and reference numeral 25 denotes a mirror for directing the light beam from the polarizing beam splitter 24 to the objective lens 26.
Referring now to FIG. 6 of the accompanying drawings which is a diagram for illustrating the control loops of auto-tracking control and auto-focusing control, reference numerals 28-30 designate the photodetectors shown in FIG. 3, and reference numeral 112 denotes a photoelectric converting part for converting the output currents of the photodetectors into electrical signals. Reference numeral 11 designates an AT/AF control circuit comprising a tracking control circuit 110 and a focusing control circuit 111. The photodetectors 28 and 30 detect light beams reflected from the tracking tracks 37 and 38 shown in FIG. 4, and the output currents of the photodetectors 28 and 30 are converted into voltage signals by current-voltage converters 5 and 6, respectively, in the photoelectric converting portion 112, and thereafter are sent to the tracking control circuit 110. In the tracking control circuit 110, the difference between said two output signals is taken, and that tracking error signal is applied to the AT actuator 16 shown in FIG. 2. That is, the AT actuator 16 is driven by the use of the tracking error signal having the tracking control loop from photodetectors 28 and 30 to the AT actuator 16 and indicative of the amount of deviation of the light spot relative to the track, and the objective lens 26 is moved in the tracking direction to thereby effect tracking control which causes the light spot to follow the information track.
The photodetector 29 is a four-division sensor as described in connection with FIG. 5, and the sum signal of the detecting pieces A and D thereof and the sum signal of the detecting pieces B and C thereof are converted into voltage signals by current-voltage converters 3 and 4, respectively, and thereafter are sent to the focusing control circuit 111. Here, the difference between the two signals is taken and is applied as a so-called focusing error signal to the AF actuator 15 shown in FIG. 2. Accordingly, the focusing control loop from the photodetector 29 to the AF actuator 15 is formed, and the AF actuator 15 is driven on the basis of the focusing error signal, whereby focusing control for focusing the light spot is effected.
The current-voltage converters 3-6 are designed such that two feedback resistors R.sub.R and R.sub.W are changed over by a switch Sw, and the feedback resistors R.sub.R and R.sub.W are changed over in conformity with a recording information signal output from the modulation-demodulation circuit 12. That is, during recording, the feedback resistors are changed over in conformity with the information signal to thereby changeover-control the gain in conformity with intensity-modulated recording light, and level control is effected so that the output of each current-voltage converter may become constant. When recorded information is to be reproduced, the light spot S2 of the three light spots shown in FIG. 4 scans the information track, and the reflected light thereof is detected by the four-division photodetector 29, whereby the recorded information is reproduced as the difference in the light intensity thereof. Although the photodetector 29 is of the four-division type, the sum total signal of the four detecting pieces thereof is used for reproduction.
Now, heretofore, the recording medium used in an information recording-reproducing apparatus has usually been limited to one kind. Therefore, the control gains of AF and AT and the reproduction gain are fixed values. Also, the driving of the semiconductor laser used as the light source is binary driving of recording power and reproduction power, and the injection current of the reproduction power and the injection current of the recording power are fixed, and these are changeover-controlled, whereby the semiconductor laser is driven.
On the other hand, there are known various information recording mediums usable in information recording-reproducing apparatuses, and for example, as a recording layer, mention may be made of metallic film such as tellurium or bismuth, organic film such as polystyrene or nitrocellulose, pigment film such as cyanin, or tellurium low oxide film utilizing phase transition. These recording materials are so-called DRAW (direct read after write) mediums which do not require the developing process after the recording of information, but permit "reading immediately after writing", and are capable of high density recording and additional recording.
However, these recording mediums are useful in their optical or chemical characteristic, but not all of them are useful when the combination thereof with an information recording-reproducing apparatus is considered. That is, as regards the optical characteristic of those recording mediums, they have a wavelength characteristic to light and even if light of the same wavelength is applied thereto, it may affect a servo control system or the like, which will thus not function normally, because they differ in reflectance. Also, the chemical characteristic will appear as a difference in reflectance because they differ in the degree of deformation or discoloration by heat. Thus, it is the present situation that the recording medium is restricted as previously described and apparatuses matching the characteristic of that medium are developed, and it has been the real situation that apparatuses cannot cope with various recording mediums.
Description will now specifically be made of the operation of an apparatus when a recording medium having other optical characteristic designated for that apparatus is set. It is to be understood that the reflectance of the recording medium is n times that of the designated recording medium. When such a recording medium is inserted into the apparatus, the quantity of light received by each photodetector becomes n times and therefore, as a matter of course, the level of each control signal subsequent to the current-voltage converter also becomes n times. However, each control gain of the apparatus is fixed and thus, each control sensitivity becomes n times. This will hereinafter be described in detail with reference to FIG. 7 of the accompanying drawings. FIG. 7 shows signals for AF AF control which are generally called S-shaped signals, signal A being the AF S-shaped signal of the recording medium designated for the apparatus, and signal B being the AF S-shaped signal of other recording medium having a reflectance of n times than the recording medium designated for the apparatus. The amplitude of the signal B is n times as great as the amplitude of the signal A because the reflectance is n times. As regards AF control, an AF actuator is controlled on the basis of this signal, but since the control gains are fixed as previously mentioned, the amount of movement of an objective lens of the signal B for the same voltage value is 1/n times the signal A, i.e., n times in terms of control sensitivity, and there occurs a phenomenon that focusing control does not function normally. Such a phenomenon occurs in an AT control system and a reproducing system as well. When a recording medium of different reflectance is thus set, control sensitivity varies, and this has led to the problem that stable AT control and AF control and reproduction become difficult and in the worst case, AT and AF are not applied at all. Also, the fact that access cannot be conducted to other recording mediums than the designated one means that the versatility as a system is spoiled, and it has been desired to solve this problem.